This invention relates to cold water swelling hydroxypropylated starches which are suitable for use in food products.
Kesler et al U.S. Pat. No. 2,516,634 discloses a method of preparing cold water swelling starch ethers by directly reacting an alkylene oxide (propylene oxide) with ordinary commercial starches containing about 10% by weight of moisture and a small amount of salt or soluble alkali, or both, incorporated in the granules. It is extremely difficult and impractical to remove the off-taste and odors from hydroxypropyl starch ethers made according to this process.
Kesler et al U.S. Pat. No. 2,845,417 discloses a method of preparing cold water gelatinizing hydroxyalkyl derivatives of unswollen granule starches and dextrins by mixing an aqueous starch slurry with a completely water-miscible alcohol and an alcohol-soluble alkali, and then reacting the starch material with a hydroxy-alkylating agent. The hydroxyalkylating agent is preferably ethylene oxide or ethylene chlorohydrin. Excess sodium chloride and sodium hydroxide impart an undesirable taste to the starch derivative.
Hanson et al U.S. Pat. No. 3,785,386 discloses a process of purifying the products derived from Kesler U.S. Pat. No. 2,516,634 and Kesler U.S. Pat. No. 2,845,417 by washing the crude reacted products with a water-alcohol mixture; the water in this mixture is present in a weight ratio of between 0.1 to 0.7 parts per part of alcohol.
Tuschhoff U.S. Pat. No. 3,705,891 discloses a method for producing ungelatinized starch derivatives suitable for human consumption by reacting propylene oxide directly with dry granular starch in the presence of a catalytic salt such as disodium or trisodium phosphate. These salts do not adversely affect the taste characteristics of the reaction product.
Kerr U.S. Pat. No. 2,733,238 discloses a process for preparing starch derivatives by treating dry starch with a volatile etherifying agent in the presence of catalytic amounts of a quaternary base, or a tertiary amine capable of forming a quaternary base by reacting with the etherifying agent. Etherifying agents contemplated by Kerr include epoxyalkanes and substituted epoxyalkanes such as ethylene oxide, propylene oxide, epichlorohydrin, etc.
It is an object of the present invention to develop a cold water swelling starch that is free of undesirable odors or off-taste.
It is a further object to develop a process for preparing cold water swelling starch that does not result in a chlorohydrin residue.
Another principal object of this invention is to prepare a cold water hydrating hydroxypropyl starch by first treating the starch with a mild chlorine treatment so as to inhibit the starch granule and thus decrease its solubility and increase its viscosity and subsequently reacting the so treated starch with propylene oxide. The mechanism of this starch inhibition is not precisely known, however it is thought that the chlorine treatment reinforces the bonding forces holding the starch granule intact, thereby inhibiting or reducing the degree of granule fragmentation on hydration. Hydrated non-fragmented starch granules bind more water, resulting in thicker sols or pastes which are thicker than sols or pastes made from hydrated fragmented starch granules. The sols or pastes of hydrated non-fragmented starch granules are characterized by short creamy textures.
These and other objects and advantages will become apparent hereinafter.